Pneumatic relay



June 20, 1967 J. w. PHILLIPS 3,326,228

PNEUMATIC RELAY Filed March 6, 1965 'no az BY M d www ATTORNEY;

United States Patent O of Delaware Filed Mar. 6, 1963, Ser. No. 263,345

-2 Claims. (Cl.` 137-86) This invention relates to pneumatic relays and more particularly to pneumatic relays including a pilot chamber. It is an object of this invention to provide a pneumatic relay having a variable bleed pilot chamber whereby the amplification ratio of the relay may be selectively varied. Still another object of this invention is to provide a pneumatic relay having a variable bleed pilot chamber including a novel variable bleed means. l These and other objects of this invention will become more fully apparent with reference to the following speciication and drawings which relate to a preferred embodiment of the invention. In the drawings:

, FIGURE 1 is a perspective of a pneumatic relay embodying the present invention;

FIGURE 2 is a schematic cross-section of the relay of FIGURE 1; and

FIGURE 3 is an enlarged detail of FIGUR-E 2.

Referring in detail to the drawings and more particularly to FIGURES 1 and 2, the relay 10 of the present invention is shown as including an outer casing 12 cornprising a base plate 14, a top end cap 16, and a plurality of pressure plates 18, 20, 22 and 24 stacked intermediate the base plate 14 and end cap 16.

A plurality of exible diaphragms 26, 28, 30 and 32 are positioned to separate the base plate 14 and the pressure plates 18, 20, 22 and 24, respectively, while the top end .cap 1-6 is separated from the upper pressure plate 24 by means of a gasket 34. v

The centers of the diaphragms 26, 28, 30 and 32 are atiixed to a common spindle 36 which is constructed of a stacked plurality of interconnected pressure discs 38, 4,0 and 42 which maintain the proper separation, respectively, between the diaphragms 26, 28, 30 and 32. The pressure discs 38, 40 and 42 are selectively proportioned with respect to the pressure plates 18, 20 and 22, respectively, whereby preselected effective areas are provided on the diaphragms 26, 28, 30 and 32 against which various pressures may be exerted.

The upper tip of the spindle 36 comprise-s a threaded shank 44 extending `upward from the vupper pressure disc 42 through the upper diaphragm 32, a spring hold-down means 46 concentric therewith and a nut 48 on said shank 44 securing said hold-down means 46 to the spindle 36 against the upper diaphragm 32.

A bi-directional bowed bias spring 50 is connected between the spring hold-down means 46 on the spindle 36, at the lower extremity thereof, and a retaining means 52 on the lower tip of a threaded, bias adjustment, set-bolt 54 which is threadably secured through the upper dome` portion 56 of the top end cap 16. A lock nut structure 58 is provided for the setbolt 54 externally of the end cap 16.

The lower tip of the spindle 36 comprises an integral exhaust valve seat y60 which is threaded into the lower pressure disc 38 and serves to secure the center of the lower diaphragm 26 thereto. The exhaust Valve seat 60 contains an exhaust bore 62 which extends therethrough and interconnects with radial bores -64 in the lower pressure disc 38.

The exhaust valve seat 60 is adapted to seat on the upper valve head 66 of a double acting relay poppet 68. The poppet 68 includes a lower head portion 70 adapted to be seated upwardly against a fixed valve seat 72 Within a supply pressure chamber 74 in the base plate 14. The supply pressure chamber 74 is fed Via an inlet coupling 76 in the base plate 14.

The relay poppet 68 is biased toward the -fxed seat 72 by means of a bowed bias spring 78 abutting an integral extension 80 on the poppet 68 and seated on an internal shoulder 82 within the supply chamber 74.

The lower diaphragm or first diaphragm 26 cooperates with the upper web 84 of the base plate 14, containing the fixed valve seat 72, to define a branch pressure chamber 86.

The first diaphragm 26 cooperates with the first pressure plate 18, rirst pressure disc-38, and the next or second diaphragm 28 to definev anexhaust chamber 88. The eX- haust chamber 88 is interconnected with the branch pressure chamber 86 via the radial ports 64 in the first pressu-re disc 38 and the exhaust bore 62 in the exhaust valve seat 60. The exhaust chamber 88 is connected to atmos phere via an exhaust port 90 in the first pressure plate 18.

The second diaphragm 28 cooperates with the second pressure plate 20, second pressure disc 40 and third diaphragm 30 to define a pilot pressure chamber 92. The pilot chamber 92 is interconnected with the branch pressure chamber 86 via a pressure transfer port 94 having an intermediate restriction 96 therein. The pilot chamber 92 is also connected with atmosphere via a variable bleed means 98, which will be hereinafter more fully described, in the second pressure plate 20.

The third diaphragm 30 cooperates with the third pressure plate 22, third pressure disc 42 and fourth diaphragm I32 to deline a'stepping chamber 100 which is connected to atmosphere vita an exhaust port 102 in the third pressure plate 2-2.

The fourth diaphragm 32 cooperates with the fourth pressure plate, gasket 34 and upper end cap'16 to detine -a signal pressurechamber 104 which may be connected in any conventional manner, not shown, to a sourceof variable signal or input pressure.

Referring jointly to FIGURES 2 and 3, the variable bleed means 98A is shown as comprising a threaded main bore 106 in the second pressure plate 28v extending inwardly 'from the outer edge thereof to a stepped-down smooth-bore inner restrictor vchamber 108, the inner chamber 108 being connected with the pilot chamber 92 via an offset bore 110 in the inner end wall 112 of the chamber 108.

Anexternally threaded restrictor'plug 1-14 is threadably inserted in the main threaded bore 106 wherein it is adjustably positioned via an Allen socket 116 (schematically shown) or the like. The restrictor plug 11`4 is provided with an axial bore 118 which is offset from the offset bore in the inner restrictor chamber 108.

The variable bleed means 98 is completed by the in-l sertion of a resilient, compressible, porous ow impeding mass 120 in the restrictor chamber 108, which is cornpressed to a selected degree between the inner end lof the restrictor plug 114 and the end wall 112 of the said restrictor chamber 108.

Operation Referring to FIGURE 2, the signal pressure in the signal chamber 104 acts on the fourth diaphragm 32 to create a downward force on the spindle 36.

The pilot pressure in the pilot chamber 92 acts on the third diaphragm 30 to create an upward force on the spindle 36 and on the second diaphragm 28 to create a -downward force on the spindle 36. The magnitude of these forces depends on the bleed rate off the variable bleed means 98 as will be hereinafter more fully described.

The vresultant of the above-defined forces causes the spindle 36 to move the integral exhaust valve seat 60 eitheir against or away from the upper head 66 of the-relay poppet 68 such that the branch pressure in the branch pressure chamber 86 is either admitted from the supply chamber 74 or exhausted therefrom via the exhaust chamber 92, respectively. Thus, equilibrium will be established such that, in the condition of balance of the relay 10, the upper head 66 of the relay poppet 68 will be seated on the exhaust valve seat 60 and the lower head 70 of the said relay poppet 68 will be seated on the fixed valve seat 72 in the supply chamber 74.

The variable bleed means 98 is controlled by turning the threaded restrictor plug 114 to vary the compression exerted thereby on the porous flow impeding mass 120, whereby t-he porosity of the said mass is varied to correspondingly vary the impedance or resistance to the flow of pressure fluid from the pilot chamber 92 to atmosphere via the offset bore 110, restrictor chamber 108 and the axial restrictor bore 118 in the said plug 114. By varying the bleed `rate of the bleed means 98, the amplification ratio or gain of the relay 10, may be selectively increased from a nominal minimum to a predetermined maximum determined by the relative effective areas of the four diaphragms 26, 28, 30 and 32.

The following equations set forth the various relationships which effect the variable gain adjustment.

Since theforce exerted by a given pressure on the spindle 36 via a given diaphragm is equal to the product of the pressure and the effective area of that diaphragm, the force equation of the relay 10, at balance, is as. follows:

Since the pilot chamber 92 is interconnected with the branch pressure `chamber 86, the pilot pressure PP is proportionally related to the branch pressure PB as a function of the bleed rate of the bleed means 98, as follows:

Substituting Equation l into Equation 9, one obtains the following expression for the relay gain:

ps- XfAz-As) +144- Thus, when X :0 (maximum bleed), and in the embodiment shown A3 A2, the gain of the relay 10 is a minimum and the gain of the relay is directly proportional to the bleed factor X. Thus, by increasing the bleed factor X, the gain may be proportionately increased, until X :l is reached, at which point the gain will have been agiusted to a maximum of a function of this bleed varia e.

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In geometries in which A2 A3, the gain off the relay will be inversely proportional to the bleed factor X as may be readily seen from Equation 1l.

The set point, or zero point, of operation of the relay 10 is selectively varied via the bow spring 50. Since the bow spring 50 superimposes an effect on the force Equations 9 and 11 as set forth above, the variable bleed means provides for re-setting the relay gain to the proper value for each set point adjustment whereby linear, predictable operation over a wide selection of .proportional bands is provided.

As can be seen from the foregoing specification and drawings, this invention provides a novel variable gain adjustment for pneumatic relays in the form of a novel variable bleed means combined with a feedback or pilot chamber in the relay.

It is to be understood that the embodiment of the invention shown and described herein is for the purpose of example only and is not intended to limit the scope of the appended claims.

What is claimed is:

1. In a pneumatic relay including a signal pressure chamber, a branch pressure chamber and a pilot chamber interconnected with said branch pressure chamber and means for varying the pressure in. said branch pressure chamber in reseponse to and as a function. of varying pressures in said signal pressure chamber, said pilot charnber being in communication with said branch pressure chamber, said chambers lbeing defined by a plurality of diaphragms, said means for varying the pressure in said branch pressure chamber including a relay spindle comrnonly connected with said diaphragms, the various diaphragms being constructed and arranged such that a change in pressure in the signal chamber effects a force on the defining diaphragm means of the latter in a direction to cause the means for varying the ypressure in said branch pressure chamber to effect a corresponding change in the branch pressure, a change of pressure in said .pilot chamber effects a force on the defining diaphragm means of the latter in a direction to cause the means for varying the branch pressure to effect a corresponding change in the said branch pressure and a change of pressure in said branch pressure chamber effects a force on the said defining diaphragm means of the latter in a direction to cause the means for varying the branch .pressure to oppose the said change in branch pressure, means for selectively varying the gain of said relay comprising a varilrble bleed means interconnecting said pilot chamber with the atmosphere, wherein said pilot chamber includes a defining side wall, and wherein said variable bleed means comprises a threaded bore in said wall open at one end to the atmosphere, a chamber at the other end of said threaded bore, a threaded plug threadably received in said bore, a compressible resilient, porous mass in said chamber compressibly engageable with said plug, an axially disposed bore in said plug interconnecting said chamber with the atmosphere and a pressure port, offset from said axially `disposed bore, interconnecting said chamber with said pilot chamber.

.2. A pneumatic `relay comprising a supply chamber, a branch pressure chamber, amodulating relay valve interconnecting said supply chamber with said branch pressure chamber and said branch pressure chamber with the atmosphere, a signal chamber, first opposed diaphragm means respectively defining a wall portion of said signal chamber and a wall portion of said branch pressure chamber, a common relay spindle interconnecting said diaphragm means and arranged to control said relay valve in response to the resultant movement of said spindle effected by said diaphragm means, a pilot chamber including second opposed diaphragm means of respectively `different effective areas interconnected byl said spindle land disposed, respectively, adjacent said rst opposed diaphragm means, .pressure transfer means interconnecting said pilot chamber 'and said branch pressure chamber and variable bleed means interconnecting said pilot chamber with the atmosphere; wherein said pilot chamber includes a dening side wall, and wherein said variable bleed means comprises a threaded bore in said wall open at one end to the atmosphere, a chamber at the other end of said threaded bore, a threaded plug threadably received in said bore, a compressible resilient, porous mass in said chamber compressibly engageable with said plug, an axially disposed bore in said plug interconnecting said chamber with the atmosphere and a pressure port, off-set from said axially disposed bore, interconecting said chamber with said pilot chamber.

References Cited UNITED STATES PATENTS Harrison 236-82 Moore 236-82 Lewis 137-86 Bjorklund 13S-43 X Berger 73-49.2

ALAN COHAN, Primary Examiner. ISADOR WEIL, WILLIAM F. ODEA,

Assistant Examiners. 

1. IN A PNEUMATIC RELAY INCLUDING A SIGNAL PRESSURE CHAMBER, A BRANCH PRESSURE CHAMBER AND A PILOT CHAMBER INTERCONNECTED WITH SAID BRANCH PRESSURE CHAMBER AND MEANS FOR VARYING THE PRESSURE IN SAID BRANCH PRESSURE CHAMBER IN RESPONSE TO AND AS A FUNCTION OF VARYING PRESSURES IN SAID SIGNAL PRESSURE CHAMBER, SAID PILOT CHAMBER BEING IN COMMUNICATION WITH SAID BRANCH PRESSURE CHAMBER, SAID CHAMBERS BEING DEFINED BY A PLURALITY OF DIAPHRAGMS, SAID MEANS FOR VARYING THE PRESSURE IN SAID BRANCH PRESSURE CHAMBER INCLUDING A RELAY SPINDLE COMMONLY CONNECTED WITH SAID DIAPHRAGMS, THE VARIOUS DIAPHRAGMS BEING CONSTRUCTED AND ARRANGED SUCH THAT A CHANGE IN PRESSURE IN THE SIGNAL CHAMBER EFFECTS A FORCE ON THE DEFINING DIAPHRAGM MEANS OF THE LATTER IN A DIRECTION TO CAUSE THE MEANS FOR VARYING THE PRESSURE IN SAID BRANCH PRESSURE CHAMBER TO EFFECT A CORRESPONDING CHANGE IN THE BRANCH PRESSURE, A CHANGE OF PRESSURE IN SAID PILOT CHAMBER EFFECTS A FORCE ON THE DEFINING DIAPHRAM MEANS OF THE LATTER IN A DIRECTION TO CAUSE THE MEANS FOR VARYING THE BRANCH PRESSURE TO EFFECT A CORRESPONDING CHANGE IN THE SAID BRANCH PRESSURE AND A CHANGE OF PRESSURE IN SAID BRANCH PRESSURE CHAMBER EFFECTS A FORCE ON THE SAID DEFINING DIAPHRAGM MEANS OF THE LATTER IN A DIRECTION TO CAUSE THE MEANS FOR VARYING THE BRANCH PRESSURE TO OPPOSE THE SAID CHANGE IN BRANCH PRESSURE, MEANS FOR SELECTIVELY VARYING THE GAIN OF SAID RELAY COMPRISING A VARIABLE BLEED MEANS INTERCONNECTING SAID PILOT CHAMBER WITH THE ATMOSPHERE, WHEREIN SAID PILOT CHAMBER INCLUDES A DEFINING SIDE WALL, AND WHEREIN SAID VARIABLE BLEED MEANS COMPRISES A THREADED BORE IN SAID WALL OPEN AT ONE END TO THE ATMOSPHERE, A CHAMBER AT THE OTHER END OF SAID THREADED BORE, A THREADED PLUG THREADEDLY RECEIVED IN SAID BORE, COMPRESSIBLE RESILIENT, POROUS MASS IN SAID CHAMBER COMPRESSIBLY ENGAGEABLE WITH SAID PLUG, AN AXIALLY DISPOSED BORE IN SAID PLUG INTERCONNECTING SAID CHAMBER WITH THE ATMOSPHERE AND A PRESSURE PORT, OFFSET FROM SAID AXIALLY DISPOSED BORE, INTERCONNECTING SAID CHAMBER WITH SAID PILOT CHAMBER. 